Parallel kinematic micromanipulator

ABSTRACT

A method and an apparatus for providing nanometer precision motion are provided. According to the invention, a parallel kinematic micromanipulator is formed using at least three kinematic links. The kinematic links may include a high resolution, non-contact encoder to provide position information. Movement of the micromanipulator is effected using piezoelectric linear actuators provided in connection with each of the kinematic links. The combination of a parallel kinematic structure and piezoelectric linear actuators provides a micromanipulator capable of positioning components or instruments with high accuracy or repeatability. In accordance with the present invention, kinematics of three and six degrees of freedom may be provided.

RELATED APPLICATIONS

[0001] This application is a continuation of prior application Ser. No.10,014,956, filed Dec. 10, 2001, entitled Parallel KinematicMicromanipulator, which is incorporated by reference into thisapplication.

FIELD OF THE INVENTION

[0002] The present invention relates to a device for positioningcomponents with high precision. In particular, the present inventionrelates to a parallel kinematic manipulator capable of positioningcomponents with nanometer tolerances.

BACKGROUND OF THE INVENTION

[0003] The precise positioning of components is increasingly important.For instance, optical communications systems require that the ends ofoptical fibers be precisely aligned with mating components or fibers toensure minimal transmission losses. The precision alignment ofcomponents is also important in connection with the manufacture ofsemiconductor devices, and with devices having miniaturized componentsand/or fine tolerance requirements. As yet another example, precisionsurgery applications, including remote surgery, require the ability toprecisely control the position and movement of instruments. However,previous attempts at providing for the precise positioning of acomponent or instrument have been incapable of providing high resolutionpositioning. In particular, previous attempts at providing devicescapable of precisely positioning components and instruments have beenincapable of providing a desired number of degrees of freedom incombination with a desired positioning tolerance.

[0004] Manipulators or positioners capable of providing a number ofdegrees of freedom are available. One such type of device is amanipulator having stacked stages. An example of a manipulator 100incorporating stacked stages is illustrated in FIG. 1. The manipulator100 includes first 104, second 108 and third 112 linear stages forproviding linear movement of the mobile plate or tool plate 116 relativeto the base plate 120. In particular, the linear stages 104, 108 and 112provide movement of the mobile plate 116 with respect to the base plate120 along the x, y and z axes. In addition, a first 124 and second 128rotational stage are provided to rotate the mobile plate 116 withrespect to two separate axes. The combination of three linear stages104, 108 and 112 and two rotational stages 124 and 128 provides amanipulator 100 having five degrees of freedom.

[0005] Although the manipulator 100 is capable of providing fivedifferent movements for positioning a component or instrumentinterconnected to the mobile plate 116, the resolution or step size withwhich such positioning can be accomplished is limited. In particular,manipulators having stacked stages, such as the manipulator 100illustrated in FIG. 1, suffer from additive positioning errors.Specifically, there are sine and cosine position errors associated witheach movement, in addition to linear (or rotational) position errors.Errors associated with each stage can contribute additively to anoverall positioning error associated with the manipulator. As a result,even if great efforts are made to accurately control the position ofeach stage, the overall positioning error remains relatively high. Forexample, if each linear actuator has an error of 50 nm, the overallpositioning error of the manipulator is likely to be at least 150 nm.Adding in errors associated with the rotational stages, and sine andcosine errors, a high quality, 5 degree of freedom manipulator 100having stacked stages is likely to have 250 nm or more of positionerror.

[0006] Parallel mechanisms provide a manipulator structure that avoidsadditive errors. In a parallel mechanism, such as the parallel mechanism200 illustrated in FIG. 2, a base plate 204 is interconnected to amobile plate 208 by a plurality of kinematic links 212. In the parallelmechanism 200 illustrated in FIG. 2, six kinematic links 212 a-f areprovided. As a result, the parallel mechanism manipulator 200, alsoknown as a hexapod, is capable of moving the mobile plate (tool plate)208 with six degrees of freedom (x, y, z, φ, θ, ψ). Because the positionerror of a parallel mechanism is not additive, higher positioningtolerances are possible than with a stacked stage type device (e.g.,manipulator 100 in FIG. 1). For example, if positioning resolutions of50 nm are available with respect to each kinematic link, a parallelmechanism type manipulator such as the manipulator 200 illustrated inFIG. 2 might be capable of positioning the mobile plate 208 with aresolution that is also about equal to 50 nm. Although such resolutionis acceptable in many cases, it is still too high for may applications,particularly aligning fiber optic cables. At the same time, it is alsodesirable to provide actuators capable of operating at high velocities,for example, to speed up production processes. Typical actuators includeservo motors, linear motors and inch worm type ceramic actuators.

[0007] Servo motor type actuators may suffer from backlash associatedwith the screw-type jacking mechanisms often used to effect changes inthe length of the kinematic link. In addition, servo and linear motortype actuators suffer from dithering, which involves high frequency,small amplitude movements of the motor as it searches for the correctposition. Such dithering can result in vibrations that can interferewith intended positioning operations, even when changes in the lengthsof the kinematic links are not being effected.

[0008] Inch worm-type piezoelectric motors generally include a pair ofceramic rings capable of selectively engaging a rod running through therings. In particular, the ceramic rings can be electrically excited insuch a way as to controllable move the rod with respect to the rings.Although such devices are capable of providing small changes in thelength of a kinematic chain, they suffer from inaccuracies due tohysteresis. Therefore, it is difficult to accurately control the lengthof a kinematic chain utilizing an inch worm-type piezoelectric actuator.The operation of such devices is also relatively slow. In addition, theoperation of inch worm-type piezoelectric actuators creates vibrationsthat can interfere with the intended positioning operations.

[0009] Therefore, there is a need for a method and apparatus capable ofproviding for the precise positioning of a component or instrument. Inparticular, there is a need for a method and apparatus for providing amanipulator capable of positioning a component or instrument with highrepeatability, resolution, and speed, without dither.

SUMMARY OF THE INVENTION

[0010] In accordance with the present invention, a parallel kinematicmicromanipulator is disclosed. Also disclosed is a method for preciselypositioning a component or instrument. The method and apparatus of thepresent invention allows for the positioning of components andinstruments with extremely high repeatability and allows multipledegrees of freedom in the movement of a component or instrument.

[0011] The inventor of the present invention has recognized that higherpositioning resolutions than are available using prior art manipulatorswould require kinematic links capable of having their lengths controlledwith greater precision. Furthermore, the inventor of the presentinvention has recognized that the inaccuracies encountered with respectto the position of individual kinematic links are in large part due tothe inaccuracies inherent to the actuators used to control the length ofthe kinematic links. Such actuators have included servo motors, linearmotors, and inch worm-type ceramic actuators. In contrast, the presentinvention comprises linear piezoelectric actuator assemblies capable ofproviding movement with resolutions that have not been available inconnection with conventional manipulators. As can be appreciated by oneof skill in the art, piezoelectric actuators take advantage of thepiezoelectric effect exhibited by certain crystals, in which theapplication of an electric field causes the crystal to expand orcontract in certain directions. Furthermore, the linear piezoelectricactuator assemblies utilized in connection with the present inventionare capable of providing motion that is substantially continuous, asopposed to the intermittent, start-stop type motion provided by inchworm type piezoelectric devices.

[0012] In accordance with an embodiment of the present invention, aparallel mechanism comprising at least three kinematic links isprovided. Each kinematic link comprises at least a first piezoelectriclinear actuator capable of providing repeatable movement of itsrespective link with a resolution of no more than about 10 nm. Such amicromanipulator is capable of positioning components or devices withvery high repeatability and resolution and can provide at least threedegrees of freedom.

[0013] According to another embodiment of the present invention, amicromanipulator comprising a hexapod type parallel mechanism isprovided. Furthermore, each of the six kinematic links of the hexapodcomprises a piezoelectric linear actuator assembly. The combination ofthe parallel mechanism configuration with piezoelectric actuatorsresults in a micromanipulator capable of providing movements havingresolutions of 10 nm or less. In addition, such an embodiment of thepresent invention is capable of providing a micromanipulator having sixdegrees of freedom.

[0014] According to a further embodiment of the present invention,parallel mechanisms are provided comprising a plurality of kinematiclinks. Each kinematic link comprises a piezoelectric linear actuatorassembly comprising at least two piezoelectric ceramic elements.According to still another embodiment of the present invention, thepiezoelectric linear actuator assemblies each comprise at least a firstrectangular piezoelectric ceramic element interconnected to a carriermember and having a plurality of electrodes that can be excited toproduce controlled movement of a slide member. According to yet anotherembodiment of the present invention, the piezoelectric linear actuatorassemblies comprise dual mode standing wave motors.

[0015] In accordance with another embodiment of the present invention, amethod for precisely positioning components or instruments is provided.According to the method, a mobile plate is interconnected to a baseplate by a plurality of kinematic links. Each of the kinematic linkscomprises at least a first piezoelectric linear actuator assembly. Afirst component or instrument is interconnected to the mobile plate,while a second component, assemblage or body is placed in a fixedposition relative to the base plate. Electrical excitation isselectively provided to a plurality of the piezoelectric linear actuatorassemblies to effect movement of the mobile plate with respect to thebase plate. In particular, electrical excitation is selectively providedto the piezoelectric linear actuator assemblies to move the component orinstrument interconnected to the mobile platform in any of a pluralityof directions. In accordance with an embodiment of the presentinvention, movement may be provided along any one of three axes.According to still another embodiment of the present invention,translational movement may be provided with respect to three axes, androtational movement may be provided about any of the three axes.

[0016] Based on the foregoing summary, a number of salient features ofthe present invention are readily discerned. A micromanipulator capableof controlled movement in a variety of directions is provided. Theamount of movement may be controlled with a high degree of precision andrepeatability. The present invention is well-suited for applicationsrequiring the alignment of precision componentry, such as in connectionwith the alignment of optical fibers. In addition, the present inventionis well suited to applications requiring precisely controlled movements,such as surgical applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a perspective view of a manipulator having stackedstages in accordance with the prior art;

[0018]FIG. 2 is an elevational view of a hexapod manipulator inaccordance with the prior art;

[0019]FIG. 3 is a perspective view of a parallel mechanism manipulatorin accordance with an embodiment of the present invention;

[0020]FIG. 4 is a top view of the parallel mechanism manipulatorillustrated in FIG. 3, with the mobile plate shown in a first position;

[0021]FIG. 5 is a side view of the parallel mechanism manipulatorillustrated in FIG. 3, with the mobile plate shown in a first position;

[0022]FIG. 6A is a plan view of a kinematic link in accordance with anembodiment of the present invention with the kinematic link shown in afirst position;

[0023]FIG. 6B is a cross-section of the kinematic link illustrated inFIG. 6A;

[0024]FIG. 7 is a plan view of the kinematic link illustrated in FIG.6A, with the kinematic link shown in a second position;

[0025]FIG. 8A is a plan view of a piezoelectric ceramic element inaccordance with an embodiment of the present invention, with the ceramicelement shown in a first position;

[0026]FIG. 8B is a plan view of the piezoelectric ceramic elementillustrated in FIG. 8A, with the ceramic element shown in a secondposition;

[0027]FIG. 9A is a front elevational view of the parallel mechanismmanipulator illustrated in FIG. 3, with the top plate shown in a secondposition;

[0028]FIG. 9B is a side elevational view of the parallel mechanismmanipulator illustrated in FIG. 3, with the top plate shown in a secondposition;

[0029]FIG. 10 is a functional block diagram depicting a systemincorporating a parallel mechanism in accordance with the presentinvention;

[0030]FIG. 11 is a flow chart depicting the operation of a systemutilizing a parallel mechanism manipulator in accordance with anembodiment of the present invention; and

[0031]FIG. 12 is a perspective view of a parallel mechanism manipulatorin accordance with another embodiment of the present invention.

DETAILED DESCRIPTION

[0032] With reference now to FIGS. 3, 4 and 5, a parallel mechanismmanipulator comprising piezoelectric linear actuator assemblies inaccordance with an embodiment of the present invention is illustrated.In general, the manipulator 300 includes a base plate 304 and a mobileplate or tool plate 308 interconnected to one another by at least threekinematic links 312. In the embodiment illustrated in FIGS. 3, 4 and 5,six kinematic links 312 are used to interconnect the base plate 304 tothe mobile plate 308. Accordingly, the manipulator 300 illustrated inFIGS. 3, 4 and 5 is a hexapod type parallel mechanism. As shown in FIGS.3, 4 and 5, the mobile plate 308 is in a first position, in which themobile plate 308 is parallel to the base plate 304, and in which thecenter point of the mobile plate 308 is aligned along the Z-axis withthe center point of the base plate 304.

[0033] Each kinematic link 312 is interconnected to the base plate 304at a first joint 316, located at a first end of each kinematic link 312.In general, the first joint 316 allows the angle of the kinematic link312 with respect to the base plate 304 to be varied. In the embodimentillustrated in FIG. 3, the first joint 312 comprises a universal joint320 and a thrust bearing 324. At a second end of each kinematic link 312a second joint 328, such as a universal joint 330, may be provided tointerconnect each kinematic link 312 to the mobile plate 308 and toallow the associated kinematic link 312 to move relative to the mobileplate 308. According to another embodiment of the present invention, oneor both of the first 316 and second 328 joints comprise sphericaljoints.

[0034] In accordance with the present invention, the first joints 316are located about a circle having a first diameter. In addition, thesecond joints 328 are located about a circle having a second diameterthat is different than the first diameter of the circle about which thefirst joints 316 are located. The arrangement of the opposite ends ofthe kinematic links 312 about circles of different diameters allowstranslational movement of the mobile plate 308 in the x and ydirections.

[0035] In addition, the interconnections between the kinematic links 312and the base plate 304 and the mobile plate 308 in the embodimentillustrated in FIGS. 3, 4 and 5 are arranged to allow rotationalmovement of the mobile plate about the z-axis. In particular, thekinematic links 312 are interconnected to the plate 304 and 308 suchthat the first end of a first kinematic link 312 is in close proximityto the first end of a second kinematic link 312, and the second end ofthe first kinematic link 312 is in close proximity to the second end ofa third kinematic link 312. For example, in FIG. 5, the first end of thefirst kinematic link 312 a can be seen to be interconnected to the baseplate 304 at a position that is in close proximity to the position atwhich the first end of the sixth kinematic link 312 f is interconnectedto the base plate 304. In addition, the second end of the firstkinematic link 312 a is interconnected to the mobile plate 308 at aposition that is in close proximity to the position at which the secondend of the second kinematic link 312 b is interconnected to the mobileplate 308.

[0036] In general, the position of the mobile plate 308 is varied withrespect to the base plate 304 by varying the lengths of the kinematiclinks 312. By coordinating the movement of individual kinematic links312, the mobile plate or tool plate 308 may be moved with respect to thebase plate 304 in six degrees of freedom.

[0037] As can be appreciated by one of ordinary skill in the art, amanipulator having six degrees of freedom is capable of translationalmovement along the x, y and z axes, as well as rotational movement abouteach of the x, y and z axes. These rotational movements, also referredto as pitch, yaw and roll, are shown as angular rotations φ, θ, and ψ onthe coordinate system illustrated in FIG. 3.

[0038] Each kinematic link 312 comprises a carrier assembly 332 and aslide assembly 336. The carrier assembly 332 may include a piezoelectriclinear actuator assembly 340 and an encoder sensor 344. The slideassembly 336 generally includes a traction surface 348, such as a stripof ceramic material that is operated on by the piezoelectric linearactuator assembly 340 to move the slide assembly 336 relative to thecarrier assembly 332. In addition, the slide assembly 336 may include anencoder strip 352 that is read by the encoder sensor 344 to determinethe position of the slide assembly 336 relative to the carrier assembly332. From the relative position of the carrier assembly 332 and theslide assembly 336, the length of the kinematic link 312 can bedetermined. It will be noted that the various components of thekinematic links 312 are arranged such that the mass of the slideassembly 336 is relatively small. By keeping the mass of the slideassembly 336 small, the inertia of the components of the manipulator 300moved during positioning operations is reduced, increasing the accuracywith which the position of the mobile plate 308 can be controlled.

[0039] In the embodiment of the present invention illustrated in FIGS.3, 4 and 5, the mobile plate 308 is relieved in an area between a secondend of the first kinematic link 312 a and the second end of the sixthkinematic link 312 f. Although not required, relieving an area of themobile plate 308 facilitates use of the manipulator 300 in connectionwith the positioning of long components, such as fiber optic cables. Themobile plate 308 may also include a recess 356 and attachment points 360to facilitate the receipt and positioning of attachment plates or chucksused to receive a component or instrument. Likewise, the base plate 304may be provided with attachment points 364 for fixing the position ofthe base plate 304 with respect to a component, assemblage or body withrespect to which the component or instrument interconnected to themobile plate 308 is to be positioned and/or moved. The attachment points360 and 364 may include, but are not limited to, mechanical fastening orindexing components, such as studs or holes, both threaded and smoothbore.

[0040] With reference now to FIG. 6A, an individual kinematic link 312is illustrated in plan view. In FIG. 6A, the carrier assembly 332 andthe slide assembly 336 are shown in a position of maximum overlap, suchthat the overall length of the kinematic link 312 is at a minimum.

[0041]FIG. 6B illustrates a cross section of the kinematic link 312shown in FIG. 6A, taken along section line A-A in FIG. 6A. In FIG. 6B,the prismatic joint 600 between the carrier assembly 332 and the slideassembly 336 that allows the length of the kinematic link to be alteredis visible. In accordance with an embodiment of the present invention,the prismatic joint 600 is formed by cross roller bearings 602. Ingeneral, the bearings 602 allow translational movement between thecarrier assembly 332 and the slide assembly 336 so that the overalllength of the kinematic link 312 can be varied, while allowing verylittle or zero movement between the carrier assembly 332 and the slideassembly 336 in directions that are not parallel to major axis (i.e. thelength) of the kinematic link 312.

[0042] Also visible in FIG. 6B are the traction surfaces 348. In theembodiment illustrated in FIG. 6B, the traction surfaces 348 areprovided on opposite sides of the slide assembly 336. The tractionsurfaces 348 are operated on by the piezoelectric linear actuatorassembly 340. In the embodiment illustrated in FIGS. 3-6, the actuatorassembly 340 comprises a pair of piezoelectric ceramic elements 604having a finger 608 interconnected to a first edge thereof. The fingers608 bear on the traction surfaces 348, to move the slide assembly 336relative to the carrier assembly 332, as will be described in greaterdetail below. In accordance with an embodiment of the present invention,the finger 608 is formed from a ceramic material.

[0043] With reference now to FIG. 7, the kinematic link 312 shown inFIG. 6 is illustrated in plan view, with the slide assembly 336 extendedrelative to the carrier assembly 332. Accordingly, configured asillustrated in FIG. 7, the kinematic link 312 is at a maximum length.

[0044] With reference now to FIGS. 8A and 8B, a large face 800 of apiezoelectric ceramic element 604 included as part of a piezoelectriclinear actuator assembly 340 in accordance with an embodiment of thepresent invention is illustrated in plan view. Also shown is the finger608 interconnected to a first edge 804 of the piezoelectric ceramic 604in contact with the traction surface 348 of the slide assembly 336.First 808, second 812, third 816 and fourth 820 electrodes are formed onthe surface of the piezoelectric ceramic element 604. A single electrode(not shown) is formed on the large face of the piezoelectric ceramicelement 604 opposite the face 800 visible in FIGS. 8A and 8B. Thissingle electrode is grounded.

[0045] The dimensions of the piezoelectric ceramic element 604 arechosen so that the resonances of the piezoelectric ceramic element 604in the x and y directions are closely spaced and have overlappingexcitation curves. For example, in the y dimension, the piezoelectricceramic element 604 may have a one-half mode resonance, and in the xdirection, the piezoelectric ceramic element 604 may have a one andone-half mode resonance.

[0046] The slide assembly 336 is moved relative to the carrier assembly332 by selectively exciting the electrodes 808, 812, 816 and 820 suchthat the finger 608 acts upon the traction surface 348 to move the slideassembly 336 relative to the carrier assembly 332. For example, byelectrically exciting diagonally opposed electrodes (e.g., electrodes812 and 816), at a frequency within the resonance band of thepiezoelectric ceramic element 604 in the x and y directions, thepiezoelectric ceramic element 604 shortens in the x direction when thechange in the y dimension of the piezoelectric ceramic 604 is positive.Accordingly, when so excited, the traction surface 348 and in turn theslide assembly 336 is moved in the negative x direction (leftward inFIGS. 8A and 8B) when movement of the piezoelectric ceramic 604 isconstrained. Conversely, electrodes 808 and 820 can be electricallyexcited while electrodes 812 and 816 are left floating or grounded, toproduce movement of the slide assembly 336 in a positive x direction (tothe right in FIGS. 8A and 8B).

[0047] The distortion of the shape of the piezoelectric ceramic element604 in response to electrical excitation of diagonally opposedelectrodes is illustrated in FIG. 8B, with the change in dimensionsgreatly exaggerated. In general, the change in dimension of thepiezoelectric ceramic element 604 per cycle of electrical excitation ofdiagonally opposed electrodes results in a very small ellipticaltrajectory at the edge 804 interconnected to the finger 608.Accordingly, actuators 340 so constructed are known as dual modestanding wave motors. Because the movement of the finger 608 is small,the movement of the traction surface 348 with respect to thepiezoelectric ceramic 604 can be very precisely controlled. In addition,because in a preferred embodiment the finger 608 is in continuouscontact with the traction surface 348, the piezoelectric ceramicactuator assemblies 340 of the present invention provide a brakingforce, resisting movement of the slide assembly 336 relative to thecarrier assembly 332, even when electrical power is not supplied to theactuator assembly 340. For additional description of a piezoelectriclinear actuator suitable for use in connection with the presentinvention, see U.S. Pat. No. 5,453,653, issued Sep. 26, 1995, and U.S.Pat. No. 5,616,980, issued Apr. 1, 1997, the entire disclosures of whichare hereby incorporated herein by reference. In accordance with anembodiment of the present invention, the piezoelectric ceramic actuatorassemblies 340 are precision dual mode standing wave motors availablefrom Nanomotion, Inc.

[0048] As an alternative to a dual mode standing wave motor, thepiezoelectric linear actuator assemblies 340 may comprise direct drivepiezoelectric motors. Direct drive piezoelectric motors are suitable foreffecting small changes in the length of the kinematic links 312, butare generally not suitable for effecting large movements. Other actuatorassemblies 340 capable of providing the required repeatability include,but are not limited to ceramic piezoelectric motors using lead screws.

[0049] With reference now to FIGS. 9A and 9B, a manipulator 300 inaccordance with the present invention is illustrated, with the top plate308 tilted and shifted with respect to the base plate 304. In general,the position of the mobile plate 308 with respect to the base plate 304can be altered by selectively altering the length of the kinematic links312. Furthermore, an embodiment having six kinematic links 312, asillustrated in FIGS. 9A and 9B, permits movement of the mobile plate 308with respect to the base plate 304 with six degrees of freedom. Inaddition, it should be appreciated that manipulators having more thansix kinematic links 312 are included in the present invention. Althoughgreater than six degrees of freedom in the movement of the mobile plate308 with respect to the base plate 304 are not provided by such adevice, the force with which the mobile plate 308 can be moved isgreater than with a manipulator having a lesser number of kinematiclinks 312, assuming that each device uses kinematic links 312 havingactuator assemblies 340 capable of individually asserting the sameamount of force. However, the inclusion of additional kinematic links312 complicates control of the position of the mobile plate 308 relativeto the base plate 304.

[0050] In FIGS. 9A and 9B, an attachment plate 900 is showninterconnected to the mobile plate 308. The attachment plate 900 mayfunction as an adaptor to facilitate the interconnection of a componentor instrument to the mobile plate 308.

[0051] In general, to effect movement of the mobile plate 308 withrespect to the base plate 304, each of the kinematic links 312 must bemoved in a coordinated fashion. In particular, for a hexapodmanipulator, such as manipulator 300 illustrated in FIGS. 3-5 and 9, sixseparate equations must be solved. In general, the desired length of thekinematic links 312 is determined by a controller interconnected to theactuators assemblies 340. In addition, the controller receivesinformation from the encoders 344 regarding the length of each kinematiclink 312 at any particular moment in time.

[0052] With reference now to FIG. 10, a block diagram depicting a system1000 incorporating a manipulator 300 in accordance with an embodiment ofthe present invention is illustrated. In general, in addition to themanipulator 300, the system includes a controller 1002 and an amplifier1004. The controller 1002 may comprise a microcontroller or centralprocessing unit. For example, the controller 1002 may be an Acroloop,MEI, Galil, Delta Tau, or National Instruments. In general, thecontroller 1002 determines the desired position of the mobile plate 308with respect to the base plate 304, or receives instructions to placethe mobile plate 308 in a desired position with respect to the baseplate 304. The controller 1002 then calculates the length of eachkinematic link 312 required to achieve the desired position. In additionto placing the mobile plate 308 in a desired end position with respectto the base plate 304, it should be appreciated that the controller 1002may determine the movements of the individual kinematic links 312required to arrive at the desired end position by following a particularpath. The controller 1002 provides control commands 1004 for effectingmovement of each of the kinematic links 312 to the amplifier 1006.

[0053] The amplifier 1006 may comprise a digital to analog converter incombination with a signal amplifier in order to provide actuatingsignals 1008 to the actuator assemblies 340 associated with thekinematic links 312. For example, the amplifier 1006 may be a Nanomotionamplifier. The provision of control signals to the actuator. assemblies340 results in a change of position of the manipulator 300. The changein position may be detected as changes in the length of the individualkinematic links 312. In particular, the each encoder sensor 344 maysense movement of the corresponding encoder strip 352 relative to theencoder sensor 344. The encoder sensors 344 may then provide positionsignals 1112 to the controller 1002. In accordance with an embodiment ofthe present invention, the encoder sensors 344 are high resolutionoptical encoders available from Reneshaw™. Preferably, each encodersensor 344 has a resolution of at least about 10 nm. More preferably,each encoder sensor 344 has a resolution of at least about 1 nm.

[0054] With reference now to FIG. 11, a flow chart depicting theoperation of a system 1000 in accordance with an embodiment of thepresent invention is illustrated, in the context of an example. Inparticular, FIG. 11 describes the positioning and attachment of anoptical fiber to another component using a manipulator 300 in accordancewith an embodiment of the present invention.

[0055] Initially, at step 1100, the position of the base 304 is fixedrelative to the component to which the optical fiber is to be attached.Next, at step 1104, the end of the optical fiber is interconnected to anattachment plate 900, which is in turn interconnected to the mobileplate 308. At step 1108, the end of the optical fiber is placed in roughalignment with the receiving component. Such rough alignment may beperformed manually, such as by a human operator visually aligning thefiber to the receiving component, or may be performed automatically, forexample in connection with optical alignment devices.

[0056] At step 1112, a test signal is transmitted through the opticalfiber, and the strength of that signal is monitored at the receivingcomponent. At step 1116, the manipulator 300 is operated to maximize theamplitude of the transmitted signal at the receiving component. As canbe appreciated by one of skill in the art, the alignment of an opticalfiber to maximize signal amplitude may require translational changes inthe position of the optical fiber of 100 nm or less, and preferably 60nm or less. In addition, such positioning may require rotational changesin the position of the optical fiber of 10 degrees or less. Such changesin position may be performed in response to commands issued by acontroller 1002 interconnected to the manipulator 300. Once maximumamplitude of the signal at the receiving component has been achieved,the optical fiber is interconnected to the receiving component, forexample by laser or UV welding (step 1120). Monitoring of the strengthof the transmitted signal and operation of the manipulator 300 todetermine the optimal alignment of the end of the optical fiber withrespect to the receiving component can be performed in connection withsoftware available from SES Technology Integration, Inc., a division ofStress Engineering Services.

[0057] In order to achieve the desired resolutions of less than 50 nm ofrepeatability for movements that involve 6 degrees of freedom, amicromanipulator 300 in accordance with the present invention mayprovide kinematic links 312 capable of being moved in resolutions of 10nm or less. In order to facilitate the reliable and repeatable movementof individual kinematic links 312 at such resolutions, the encodersensor 344 preferably provides resolutions of 10 nm or less, and morepreferably 1 nm or less, and the piezoelectric linear actuatorassemblies 340 preferably provide resolutions of less than about 10 nm,and more preferably 1 nm or less.

[0058] In connection with applications in which six degrees of freedomare not required, a tripod configuration may be utilized. In general, atripod configuration provides translational movement along one axis, androtational movement about two axes. A manipulator 1200 having a tripodconfiguration in accordance with the present invention is illustrated inFIG. 12, and generally includes a base plate 1204 interconnected to amobile plate 1208 by three kinematic links 1212. In the embodimentillustrated in FIG. 12, the kinematic links 1212 are interconnected tothe base plate by a first joint 1216 comprising a journal bearing 1220.The first joint 1216 need only provide for rotation of a correspondingkinematic link about a single axis, because the tripod configurationdoes not permit the mobile plate 1208 to be rotated relative to the baseplate 1204 by altering the lengths of the kinematic links 312. The topjoint 1228 may comprise a universal joint 1230. As can be appreciated byone of skill in the art, a kinematic link 1212 may be interconnected tothe plates by other types of joints 1216 and 1228. For example, jointslike the joints 316 and 328 disclosed in connection with FIG. 3 may beutilized. Furthermore, the actuator assemblies 1240 and encoder sensor1244 may be like those utilized in connection with the actuatorassemblies 340 and encoder sensors 344 disclosed in connection with FIG.3.

[0059] Although the manipulator 1200 having a tripod configuration inaccordance with the present invention is capable of providing only threedegrees of freedom, it is capable of providing very high precisionrepeatability and/or movement. In particular, the manipulator 1200 mayprovide movement with a precision of 40 nm or better. Furthermore, themanufacture and control of the manipulator 1200 is simplified ascompared to manipulators having more than three kinematic links.Therefore, the manipulator 1200 may be advantageous in connection withapplications requiring extremely small positioning resolutions, in whichonly three degrees of freedom are required. Furthermore, whereadditional degrees of freedom are required, a manipulator 1200 having atripod configuration may include additional linear or rotary stages.

[0060] Although the description set forth herein has noted thepositioning of optical fibers and micro surgery as particularapplications of the present invention, the present invention is not solimited. For example, the present invention is also suitable for use inconnection with component testing, component assembly, micro-machinery,semiconductor manufacture, pharmaceutical applications, as an analyticalinstrument for use in connection with robot design, and any otherapplication where extremely precise movement, positioning, or movementand positioning of components or instruments is desirable.

[0061] The foregoing discussion of the invention has been presented forpurposes of illustration and description. Further, the description isnot intended to limit the invention to the form disclosed herein.Consequently, variations and modifications commensurate with the aboveteachings, within the skill and knowledge of the relevant art, arewithin the scope of the present invention. The embodiments describedhereinabove are further intended to explain the best mode presentlyknown of practicing the invention and to enable others skilled in theart to utilize the invention in such or in other embodiments and withvarious modifications required by their particular application or use ofthe invention. It is intended that the appended claims be construed toinclude the alternative embodiments to the extent permitted by the priorart.

1. A parallel kinematic manipulator comprising: a base plate; a mobileplate; and a plurality of kinematic links arranged in parallel betweenthe base plate and the mobile plate, wherein each one of the kinematiclinks comprises: a first joint coupling the one kinematic link to thebase plate and configured to allow the one kinematic link to moverelative to the base plate; a second joint coupling the one kinematiclink to the mobile plate and configured to allow the one kinematic linkto move relative to the mobile plate; and a piezoelectric linearactuator assembly configured to move the one kinematic link with asubstantially continuous motion.
 2. The parallel kinematic manipulatorof claim 1 wherein the piezoelectric linear actuator assembly comprisestwo piezoelectric linear motors positioned on opposite sides of the onekinematic link.
 3. The parallel kinematic manipulator of claim 1 whereinthe piezoelectric linear actuator assembly comprises two piezoelectriclinear motors in contact with the one kinematic link.
 4. The parallelkinematic manipulator of claim 1 wherein the first joint comprises athrust bearing and a universal joint
 5. The parallel kinematicmanipulator of claim 1 further comprising an encoder configured todetermine lengths of the kinematic links.
 6. The parallel kinematicmanipulator of claim 1 wherein the encoder comprises a plurality ofoptical sensors configured to detect positions of the kinematic links.7. The parallel kinematic manipulator of claim 1 further comprising acontroller configured to control lengths of the kinematic links.
 8. Theparallel kinematic manipulator of claim 1 further comprising acontroller configured to determine lengths of the kinematic links tomove the mobile plate to a desired position.
 9. The parallel kinematicmanipulator of claim 1 wherein the mobile plate is relieved.
 10. Theparallel kinematic manipulator of claim 1 wherein the mobile plate isconfigured to hold an optical fiber and the parallel kinematicmanipulator is configured to align the optical fiber.
 11. A method ofoperating a parallel kinematic manipulator comprising a base plate, amobile plate, a plurality of kinematic links, first joints coupling thekinematic links to the base plate, second joints coupling the kinematiclinks to the mobile plate, and a plurality of piezoelectric linearactuator assemblies, wherein the kinematic links are arranged inparallel between the base plate and the mobile plate, the methodcomprising: operating the piezoelectric linear actuator assemblies tomove the kinematic links with a substantially continuous motion; in thefirst joints, allowing the kinematic links to move relative to the baseplate; and in the second joints, allowing the kinematic links to moverelative to the mobile plate.
 12. The method of claim 11 whereinoperating the piezoelectric linear actuator assemblies comprisesoperating pairs of piezoelectric linear motors positioned on oppositesides of the kinematic links.
 13. The method of claim 11 whereinoperating the piezoelectric linear actuator assemblies comprisesoperating pairs of piezoelectric linear motors in contact with thekinematic links.
 14. The method of claim 11 wherein allowing thekinematic links to move relative to the base plate comprises using athrust bearing and a universal joint.
 15. The method of claim 11 furthercomprising determining lengths of the kinematic links.
 16. The method ofclaim 11 further comprising operating optical sensors to detectpositions of the kinematic links.
 17. The method of claim 11 whereinoperating the piezoelectric linear actuator assemblies to move thekinematic links comprises controlling lengths of the kinematic links.18. The method of claim 11 further comprising determining lengths of thekinematic links to move the mobile plate to a desired position.
 19. Themethod of claim 11 wherein the mobile plate is relieved.
 20. The methodof claim 11 further comprising holding an optical fiber with the mobileplate, and wherein operating the piezoelectric linear actuatorassemblies to move the kinematic links comprises aligning the opticalfiber.